Ricinoleate urethane polyols are well known in the art for use in the formulation of adhesives and coatings as plasticizers, pigment dispersing agents and tackifiers as well as a reactive ingredient.
Ricinoleate urethane polyols themselves vary in consistency from high viscosity oils to greases and, while they have some tack, they lack cohesive strength. Thus, they are not employed alone as pressure sensitive adhesives or contact cement nor do they impart cohesive strength to adhesives when used as tackifiers.
Two-package urethane adhesives which cure by the reaction of the hydroxyl groups of the ricinoleate urethane polyol with an isocyanate are strong adhesives when cured but exhibit very little green strength. "Green strength" as used herein means the ability to hold two surfaces together when first contacted and before the adhesive develops its ultimate bonding properties when fully cured.
The degree of green strength exhibited by an adhesive is vital to many applications. High green strength tends to prevent wrinkling and slippage of films during lamination. In panel assembly and packaging, it permits faster handling and wrapping. When an adhesive is applied to a vertical surface, a sufficiently high green strength prevents a mechanically unsupported, bonded member from slipping under the influence of gravity. When employed for flocking, high green strength holds fibers in place while the adhesive cures and in the laying of carpet or synthetic flooring, it resists curling due to the shape-memory thereof acquired when stored in a roll.
Two-package urethane coatings which cure by the same reaction as set forth above with respect to adhesives have good flexibility and toughness but develop film hardness slowly. It is preferable that floor coatings develop hardness sufficient to accept traffic rapidly to minimize down-time whether the coating be used on new construction or existing sites.
Additionally, when urethane coatings and adhesives are applied to concrete, it is currently necessary to acid-etch the concrete prior to application. While acid-etching of the concrete is a prerequisite for excellent adhesion, a higher degree of adhesion to concrete that has not been acid-etched is always desirable by virtue of the fact that when large areas are acid-etched frequently portions thereof are either missed or inadequately etched resulting in poor adhesion.
In accordance with the present invention, it has been found that a mixture of ricinoleate urethane polyol and chlorinated rubber exhibits a unique combination of properties which are not achievable if either product is employed alone or if either product were omitted from certain formulations containing other ingredients. Chlorinated rubber is known for its fast, tack-free dry and for that reason is often added to formulations to quickly eliminate tack which is the very antithesis of its use in adhesives claimed in the present invention resulting in new and unexpected results including converting a ricinoleate urethane polyol from a product with little tack and cohesiveness to one that is tenacious.
A chlorinated rubber/ricinoleate urethane polyol mixture in accordance with the present invention is useful in the formulation of pressure sensitive and curable adhesives, contact cements, protective coatings, curable urethanes and curable coatings. Such mixtures are also useful as tackifying additives, anti-slip additives, flexibilizing agents, cross-linking agents, adhesion improvers and the like. The term "adhesive" as used herein is intended to include broadly, adhesives, coatings and all other uses to which the combination of chlorinated rubber and ricinoleate urethane polyol may be employed.